Microelectronic devices generally have a die (i.e., a chip) that includes integrated circuitry having a high density of very small components. In a typical process, a large number of dies are manufactured on a single wafer using many different processes that may be repeated at various stages (e.g., implanting, doping, photolithography, chemical vapor deposition, plasma vapor deposition, plating, planarizing, etching, etc.). The dies typically include an array of very small bond-pads electrically coupled to the integrated circuitry. The bond-pads are the external electrical contacts on the die through which the supply voltage, signals, etc., are transmitted to and from the integrated circuitry. The dies are then separated from one another (i.e., singulated) by dicing the wafer and backgrinding the individual dies. After the dies have been singulated, they are typically “packaged” to couple the bond-pads to a larger array of electrical terminals that can be more easily coupled to the various power supply lines, signal lines, and ground lines.
An individual die can be packaged by electrically coupling the bond-pads on the die to arrays of pins, ball-pads, or other types of electrical terminals, and then encapsulating the die in a molding compound to protect it from environmental factors (e.g., moisture, particulates, static electricity, and physical impact), and to form a microelectronic device package. In one application, the bond-pads are electrically connected to contacts on an interposer substrate that has an array of ball-pads.
Electronic products require packaged microelectronic devices to have an extremely high density of components in a very limited space. For example, the space available for memory devices, processors, displays, and other microelectronic components is quite limited in cell phones, PDAs, portable computers, and many other products. As such, there is a strong drive to reduce the surface area or “footprint” of the microelectronic device on a printed circuit board. Reducing the size of the microelectronic device can be difficult because high performance microelectronic devices generally have more bond-pads, which result in larger ball-grid arrays and thus larger footprints. One technique used to increase the density of microelectronic devices within a given footprint is to stack one microelectronic device package on top of another. However, these existing stacked designs may have certain disadvantages. For example, they may require excessive space on the substrates for interconnections, preclude separate quality control testing of the devices, or have other drawbacks.